There are in the prior art a number of engine protective devices which shut off or greatly reduce the flow of fuel to the engine in the event of inadequate lubricating oil pressure. The following Patents assigned to the Assignee of the present invention, and hereby incorporated by reference, disclose such prior art devices:
______________________________________ U.S. Pat. No. Inventor Dated ______________________________________ 3,202,143 Goodwin Aug. 24, 1965 3,523,521 Goodwin Aug. 11, 1970 3,590,798 Goodwin July 6, 1971 4,117,822 Mills Oct. 3, 1978 ______________________________________
The device of U.S. Pat. No. 3,202,143 is a full fuel shut off valve effecting an automatic full shut down of the engine when the oil pressure drops below a predetermined value or the engine overheats. This device also includes a manually operable override which, when operated, will allow sufficient fuel to reach the engine to produce maximum power and speed even though the engine pressure has dropped below normal, or the engine has overheated, with possible consequent damage to the engine.
U.S. Pat. No. 3,523,521 discloses an engine safety device responsive to abnormal oil pressure conditions. The device includes means for varying the oil pressure level at which the fuel valve is shut off dependent on variations in the pressure of the fuel being supplied to the engine.
U.S. Pat. No. 3,590,798 also discloses an engine safety device responsive to abnormal oil pressure and coolant temperature conditions. However, unlike the two patented inventions discussed immediately above, this device is not a full fuel shut off effecting a full shut down of the engine. Instead, it is an automatic engine decelerating or detorquing valve by virtue of a built in fuel bypass which continues to supply the engine with a restricted quantity of fuel after the main fuel valve is closed. It also includes a manually operated override which, when operated, permits operation of the engine at maximum power and speed in like fashion to the above-described device of U.S. Pat. No. 3,202,143.
U.S. Pat. No. 4,117,822 discloses a safety device which effects a full shutdown of the engine when abnormally low oil pressure conditions arise. A manually operated override is included whereby a restricted amount of fuel sufficient only to run the engine at a reduced power and at reduced speed is supplied to the engine.
Although the devices of the prior art have been quite useful in preventing various engine damage, they have been subject to a number of undesirable limitations.
One limitation of the prior art devices, is the inability of the engine owner to determine whether the engine operator has overriden the fuel shut off valve. In particular, the prior art devices lack a means whereby the engine owner can determine whether the operator has overriden the emergency shut down. For these prior art devices, the operator may run the engine for long periods of time after actuating the override option, thereby causing severe damage to the engine. After such excessive engine damage has been caused, an unscrupulous operator may simply return the override control knob to the run position and deny having actuated the override. Due to the high cost of diesel engine repairs, engine owners are most desirous of minimizing override abuse by the operators after an emergency shut down.
A further problem with the prior art devices is the need to obtain access to the engine in order to override the engine protective shut off of the fuel flow. For certain engines it may be necessary to actuate the override for starting purposes because the fuel downstream from the fuel valve is not adequate to keep the engine going long enough to build up the oil pressure sufficiently to open the fuel valve. It is most inconvenient to have to obtain access to the engine to actuate the override for starting purposes.
A further deficiency in the prior art devices is the inability to conveniently and securely change from a detorque mode of operation (wherein failure of oil pressure causes a restricted amount of fuel flow) to a shut down mode of operation (wherein loss of oil pressure causes complete fuel cut off). Although the above-discussed U.S. Pat. No. 3,590,798 does disclose a device which may be changed from a detorque mode to a full shut down mode this change of modes may be accomplished simply by adjusting an externally accessible set screw 106. Accordingly, the operator of the engine may use such a set screw to defeat the engine owners command that the device be operated in the full shut down mode.
Although the above-mentioned U.S. Pat. No. 4,117,822 discloses a engine protective device with a restricted override, the restricted override has required mechanisms substantially different from the handle 50 and the cam 43 of such patents as U.S. Pat. Nos. 3,202,143 and 3,590,798. It would be most useful if an arrangement could be found, wherein a handle and cam such as in U.S. Pat. Nos. 3,202,143 and 3,590,798 controlled the operation of a restricted override.
U.S. patent application Ser. No. 296,193, which is the parent application to the present application, discloses a system which overcomes or minimizes these problems. However, the remote override arrangements disclosed in this parent patent application have several disadvantages.
The system in the parent application discloses an electrical override system which is readily adaptable to those engines which use battery or electric starting. However, there are a substantial number of engines for which the electrical override system is not especially well-suited.
The alternate pneumatic override disclosed in the parent application is quite useful in numerous applications. However, it is not always desirable or possible to use a pneumatic source for supplying pneumatic pressure.
If the engine protective system was installed on a vehicle with air brakes, one could "tap-in" on the pressurized air in the air brake system. Obviously, the tapping-in to use the same pressurized air for the engine protective valving apparatus as used for the brakes would have to be done very carefully. Air leaks in the system might disable the vehicle's brakes.
An engine driven air compressor could be used as a pneumatic source, but an engine is usually shut-down for hours at a time. The engine driven air compressor and the air supply or holding tanks may lose their pressure. Further, the operator may manually exhaust the air supply to avoid condensation. On those engines where the remote override must be initially operated to start the engine, the lack of air pressure would prevent the starting of the engine by an engine driven air supply.
The use of an air source not powered by the brakes or motor could avoid these disadvantages of a pneumatic override. However, this would add considerably to the complexity and cost of the system.